Fixed #29078 -- Made serializers respect prefetch_related() for m2m fields.

1 files changed, 5 insertions, 3 deletions

diff --git a/django/core/serializers/python.py b/django/core/serializers/python.py
index 5a5d8a7036..0ceb676e90 100644
--- a/django/core/serializers/python.py
+++ b/django/core/serializers/python.py
@@ -67,9 +67,11 @@ class Serializer(base.Serializer):
             else:
                 def m2m_value(value):
                     return self._value_from_field(value, value._meta.pk)
-            self._current[field.name] = [
-                m2m_value(related) for related in getattr(obj, field.name).iterator()
-            ]
+            m2m_iter = getattr(obj, '_prefetched_objects_cache', {}).get(
+                field.name,
+                getattr(obj, field.name).iterator(),
+            )
+            self._current[field.name] = [m2m_value(related) for related in m2m_iter]
 
     def getvalue(self):
         return self.objects